1. Field of the Invention
The present invention relates to a stroke characteristic variable engine, and more particularly to a stroke characteristic variable engine which can simplify the supply of lubricating oil to a piston stroke variation mechanism which includes a plurality of links.
2. Description of the Background Art
There is known a stroke characteristic variable engine in which a piston and a crankshaft are connected to each other by means of a plurality of links and a piston stroke is made to be varied by varying the position of a connecting end of one (a control link) of the links to an engine main body (refer to, for example, Japanese Patent Unexamined Publication No. JP-A-2004-116434).
In the event of the engine of this type, lubricating oil needs to be supplied to connecting portions where the respective links are connected to each other and a bearing for a control shaft which varies the position of the one of the links to the engine main body. Namely, the supply of lubricating oil needs to be increased compared to general engines.
However, since the configuration of the stroke characteristic variable engine disclosed in Patent Document No. 1 is such that the capacity of a lubricating oil pump is set for a needed volume when the engine is operated at a high compression ratio and the degree of communication of oil paths provided inside the control link and the control shaft is made to vary in accordance with a change in compression ratio in order to reduce the load to be borne by the pump when the engine is run at a low compression ratio, the number of manhours for manufacture tends to be increased due to an increase in capacity of the oil pump, as well as the complex configuration of the oil paths.